Solve for $a$ : $-20 = a - 26$
Add $26$ to both sides: $ \begin{eqnarray} \\ \hphantom{-20 {+ 26}} &\hphantom{=}& \hphantom{a} \\ -20 &=& a - 26 \\ \\ {+26} && {+26} \\ \end{eqnarray} $ $ \begin{eqnarray} \\ -20 {+ 26} &=& a \\ \end{eqnarray} $ Simplify. $ a = 6$